DESCRIPTION:The ability to detect and respond to signals from the environment and neighboring cells is of fundamental biological importance. Adaptation requires detection of the environmental stimulus, processing of the signal, and production of an appropriate response. Myxococcus xanthus provides an attractive model system for studies of intracellular and intercellular signaling. When M. xanthus senses starvation, high cell density, and a solid surface, the cells glide to aggregation centers where they form multicellular spore-filled fruiting bodies. The long term goal of this work is to determine the molecular events between starvation sensing and production of A-signal, an extracellular, cell-density signal. Three genes (asgA, asgB and asgC) that participate in the A-signal-generating pathway were identified previously. The first aim is to identify additional components of the A-signal-generating pathway. Specifically, 1)Intergenic suppressors of asgA and asgB that restore development will be isolated and characterized. 2) a candidate target gene for AsgB, a putative transcriptional regulator, will be cloned and analyzed for regulation by AsgB, and 3) in vitro and in vivo methods will be used to search for additional target genes. The second aim is to study the regulation and function of AsgA, an autokinase with an unusual domain organization, and AsgB. These studies include 1) domain liberation experiments to analyze the functions of the receiver and transmitter domains of AsgA, and 2) a test of the hypothesis that AsgA is a substrate for BsgA, a Lon-type protease. #) AsgB will be analyzed for interaction with AsgC (RpoD) using the yeast two hybrid system, and 4) the hypothesis that AsgB is phosphorylated by a serine/threonine kinase will be tested by immunoprecipitation of labeled soluble proteins from wild type and asg mutant strains. All together, these studies will allow a greater understanding of the signal transduction mechanisms and cell-cell interactions that promote the multicellular state.